Late Formation Research Articles

Source rock and petrophysical evaluation of the Late Cretaceous Haymana Formation, Haymana Basin, Central Anatolia, Turkey

This study investigates the petroleum potential of the mudstones of the Late Cretaceous Haymana Formation in the Haymana Basin, Turkey. Lithofacies, pore structure, and source rock characteristics of the mudstones are examined using stratigraphical, sedimentological, petrophysical, and organic geochemical methods along four stratigraphic sections and other sampling sites. The depositional model presents a facies distribution within a submarine fan system. According to bulk mineralogy, the identified lithofacies are mixed mudstone, mixed siliceous mudstone, marl, mixed carbonate mudstone, argillaceous/siliceous mudstone, and clay-rich siliceous mudstone. XRD and mercury intrusion measurements suggest that the macropores (> 50 nm) of the mudstones formed by dissolution of calcite, while mesopores (2 nm-50 nm) developed around the clay/quartz/feldspar. Of the analysed samples, no lithofacies class is distinct with any specific range of porosity or permeability, which suggests a strong heterogeneity in pore throat size, mineral content, and grain size. The black shale from the northwest of the basin with 1.19% TOC, 0.07 mg/g S 1 , 1.01 mg/g S 2 , and 441°C T max is a relatively more mature source rock although it still exhibits poor petroleum potential. Overall, the TOC values (avg. 0.38%) of the mudstones suggest organic-poor rock characteristics for the Haymana Formation in the studied parts of the Haymana Basin.

Comparative transcriptomic analysis validates iPSC derived in-vitro progressive fibrosis model as a screening tool for drug discovery and development in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune dysregulation, and systemic fibrosis. Research on SSc has been hindered largely by lack of relevant models to study the progressive nature of the disease and to recapitulate the cell plasticity that is observed in this disease context. Generation of models for fibrotic disease using pluripotent stem cells is important for recapitulating the heterogeneity of the fibrotic tissue and are a potential platform for screening anti-fibrotic drugs. We previously reported a novel in-vitro model for fibrosis using induced pluripotent stem cell-derived mesenchymal cells (iSCAR). Here we report the generation of a "scar-like phenotype" when iPSC derived mesenchymal cells are cultured on hydrogel that mimicks a wound healing/scarring response (iSCAR). First, we performed RNA sequencing (RNA-seq) based transcriptome profiling of iSCAR culture at 48h and 13days to characterize early and latestage scarring phenotypes. The next generation RNA-seq of these iSCAR culture at different timepoints detected expression 92% of early "scar associated" genes and 85% late "scar associated" genes, respectively. Comparative transcriptomic analysis of a gene level SSc compendium matrix to the iSCAR wound associated model revealed genes common in both data sets. Early scar formation genes showed biological processes of hypoxia (27.5%), vascular development (13.7%) and glycolysis (27.5), while late scar formation showed genes associated with senescence (22.6%). Next we show the effects of two different antifibrotic compounds to validate the utility of the model as a screening tool to study early and late-stagelate-stage fibrosis. An autotaxin inhibitor was used to validate the iSCAR late stage fibrotic model (iSCAR-T) and an antifibrotic tool screening compound of unknown mechanism (EX00015097) was used to study and validate both early (iSCAR-P) and late-stage (iSCAR-T) fibrosis in the iSCAR model.

Mechanism of low-intensity pulse ultrasound combined with Rhodiola to promote bone formation in spinal fusion.

This study aimed to explore the influence and mechanism of low-intensity pulsed ultrasound (LIPUS) combined with Rhodiola bone penetration on the formation of spinal fusion bone. Sixty clean-grade New Zealand white rabbits were selected for randomization and divided into combined group and Rhodiola group, with 30 rabbits in each group to construct a rabbit lumbar intervertebral fusion model, using Rhodiola intervention and Rhodiola combined with LIPUS intervention protocol, respectively. The axial strength, axial stiffness, maximum compressive load, vascular endothelial growth factor (VEGF), cycloxygenase-2 (COX-2), prostaglandin E2 (PGE2) and transforming growth factor-β (TGF-β) were compared after HE staining, immunohistochemistry and biomechanical detection. Spine fusion rate was 100.00%; the combined bone graft tissue had implanted bone cell degeneration, cell necrosis and cell hyperplasia, chondrocytes differentiated into trabecular bone and some hematopoietic cells, severe cell necrosis and fiber cell proliferation and late bone formation in the Rhodiola group, VEGF, COX-2, PGE2, TGF-β, axial strength, axial stiffness, and maximum compression load in the combined group significantly increased (P<0.05). Spinal fusion using LIPUS combined with Rhodiola can enhance biomechanical properties and promote the role of PGE2, COX-2, VEGF, TGF-β expression and bone formation, and this protocol is worthy of clinical application.

The mechanism of dolomitization in a stromatolite mound in the late Cambrian Chaomidian Formation, Shandong Province, China

Clarifying the mechanism of dolomitization is of pivotal importance and represents a burning issue among geologists. A comprehensive model to define the genesis of dolomitization in the Cambrian Chaomidian Formation carbonates is still lacking. In the highly focused study, the advanced integration of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), clumped isotope and carbon/oxygen isotope analyses was used to reveal complex interactions between the genesis and dolomitization of a stromatolite mound in the late Cambrian Chaomidian Formation of China. The results show that the dolomite content increases from bottom to top, along with a shift in lithology from limestone to dolostone. Additionally, as we moved from the base to the summit of the stromatolite mound, the Fe, Mn, and Na contents increase with increasing Mg levels, whereas the δ13C and δ18O values became more positive. Conversely, the levels of Sr and total rare earth elements (REEs) gradually decreased. The dolomite grains in the stromatolite mound are micritic and euhedral to subhedral, with foggy cores and bright edges and low cation ordering. The stromatolite limestone, dolostone, and underlying lime mudstone samples exhibit similar REE patterns: light REE enrichment, heavy REE loss, negative δEu anomalies, and weak negative δCe anomalies. The δ13C and δ18O values fall within the late Cambrian seawater range, suggesting that dolomitizing fluids originated mainly from concentrated seawater and migrated from top to bottom. The δ18O values indicate lower dolomite formation temperatures than calcite formation temperatures, supporting dolomitization during the penecontemporaneous diagenetic stage. Petrographic evidence reveals the presence of pyrite, indicating sulfate-reducing bacterial activity during diagenesis. XPS analysis revealed similar organic functional groups in both the stromatolite limestone and the dolostone, including C-(C = O)-O, C–C/C-(C–H), C-O and C-N. However, the dolostone spectrum exhibited a larger C-OH/C-O peak area, suggesting significant microbial organic matter involvement in dolomite formation. While a kinetic obstacle is recognized as a primary cause of dolomite formation, this study also suggested that microbial activity weakened this obstacle during diagenesis. Thus, microbial metabolism or cyanobacterial decomposition facilitates dolomite formation during the penecontemporaneous diagenetic stage.

Effect of laser remelting on the microstructures and properties of NiCoCrAlY-based coatings prepared by high-speed air fuel supersonic flame (HVAF)

In order to improve the oxidation resistance of the coating, laser remelting technology was used to remelt the HVAF multi-component modified coating. The influence of laser remelting technology on the phase state, microstructure characteristics, and isothermal oxidation behavior of coatings was studied. The experimental results indicate that a coating with complete morphology and no defects was obtained on the surface. There is a significant amount of metallurgical bonding and partial mechanical interlocking between the remelted layer and the substrate. The remelted layer is mainly composed of β-NiAl phase, accompanied by a small amount of γ′ phase and oxide phase. The microhardness test results show that the average hardness of the remelted layer is 1.1–1.42 times that of the prepared coating, and the bonding strength has increased by 23 %. After 100 h of high-temperature oxidation, the oxidation rate of the 4N3T4H remelted layer is the lowest, at 1.5 × 10−15 cm2/s, which is one order of magnitude lower than that of the as-sprayed coating. This is because after laser remelting, the remelted layer has the inherent hysteresis diffusion effect of HEA, which can improve the high-temperature oxidation resistance of the remelted layer and basically eliminate many pores and cracks contained in the HVAF coating. The coating density is significantly increased, which is conducive to hindering the diffusion of oxygen. Meanwhile, the oxide of HVAF coating mainly accumulates at pores and cracks, and there is no or late formation of uniform and dense oxide film on the surface. The surface of the remelted coating after oxidation forms a relatively uniform and dense oxide film, providing more effective protection for the substrate.

A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics

The living coelacanth Latimeria (Sarcopterygii: Actinistia) is an iconic, so-called ‘living fossil’ within one of the most apparently morphologically conservative vertebrate groups. We describe a new, 3-D preserved coelacanth from the Late Devonian Gogo Formation in Western Australia. We assemble a comprehensive analysis of the group to assess the phylogeny, evolutionary rates, and morphological disparity of all coelacanths. We reveal a major shift in morphological disparity between Devonian and post-Devonian coelacanths. The newly described fossil fish fills a critical transitional stage in coelacanth disparity and evolution. Since the mid-Cretaceous, discrete character changes (representing major morphological innovations) have essentially ceased, while meristic and continuous characters have continued to evolve within coelacanths. Considering a range of putative environmental drivers, tectonic activity best explains variation in the rates of coelacanth evolution.

Iskar Gorge and Ledenika cave - a brief overview

The Late Paleozoic and Mesozoic sequences in the Svoge, West Balkan and Fore-Balkan units (Western Bulgaria) are exposed in eight points. Most of the points are within the area of the Iskar Gorge. At point 1, SE of the village of Redina on the road to Svoge, the rocks of the Late Carboniferous Svoge Formation can be observed – terrigenous sediments of alluvial-limnic character with preserved megaflora. Triassic and Jurassic sequences are traced in the area of point 2 near the village of Zasele. Point 3 is in Triassic sediments and provides a view from the east of the Upper Carboniferous diorites of the Petrohan intrusion. Karst processes are developed in some sections of the Iskar Gorge and caves of different sizes can be seen. One of them is the Temnata Dupka Cave (point 4), which is formed in the Middle Triassic rocks of the Iskar Carbonate Group. In the area of the village of Cherepish (point 5), the lower part of the Lower Cretaceous Vratsa Urgonian Group (Cherepish Formation) is exposed. The upper level of the Vratsa Urgonian Group can be traced in the next point 6, where the geological phenomenon Ritlite (Lyutibrod Formation) is situated. In the area of the village of Chelopek (point 7), a continuous section between the Cretaceous and Paleogene is observed. Southwest of Vratsa, at point 8, the Ledenika Cave is revealed, located in the Upper Jurassic–Lower Cretaceous carbonate sediments of the Gintsi Formation.

Single-cell RNA-seq analysis of rat molars reveals cell identity and driver genes associated with dental mesenchymal cell differentiation

BackgroundThe molecular mechanisms and signaling pathways involved in tooth morphogenesis have been the research focus in the fields of tooth and bone development. However, the cell population in molars at the late bell stage and the mechanisms of hard tissue formation and mineralization remain limited knowledge.ResultsHere, we used the rat mandibular first and second molars as models to perform single-cell RNA sequencing (scRNA-seq) analysis to investigate cell identity and driver genes related to dental mesenchymal cell differentiation during the late bell hard tissue formation stage. We identified seven main cell types and investigated the heterogeneity of mesenchymal cells. Subsequently, we identified novel cell marker genes, including Pclo in dental follicle cells, Wnt10a in pre-odontoblasts, Fst and Igfbp2 in periodontal ligament cells, and validated the expression of Igfbp3 in the apical pulp. The dynamic model revealed three differentiation trajectories within mesenchymal cells, originating from two types of dental follicle cells and apical pulp cells. Apical pulp cell differentiation is associated with the genes Ptn and Satb2, while dental follicle cell differentiation is associated with the genes Tnc, Vim, Slc26a7, and Fgfr1. Cluster-specific regulons were analyzed by pySCENIC. In addition, the odontogenic function of driver gene TNC was verified in the odontoblastic differentiation of human dental pulp stem cells. The expression of osteoclast differentiation factors was found to be increased in macrophages of the mandibular first molar.ConclusionsOur results revealed the cell heterogeneity of molars in the late bell stage and identified driver genes associated with dental mesenchymal cell differentiation. These findings provide potential targets for diagnosing dental hard tissue diseases and tooth regeneration.

The influence of topography on subaqueous gravity flows: a case study from the Jurassic Los Molles Formation, Neuquén Basin, Argentina

ABSTRACT Subaqueous sediment gravity flows experience modifications when they interact with slope and basin-floor topography, impacting facies, geometries, and architectural patterns of the deposits. Understanding these processes is critical for reservoir-quality and trap predictions in deep-water stratigraphic plays. A comprehensive literature summary of the topographic influence on subaqueous gravity flows and an interpretation applied to the basin-floor turbidite system of the late synrift Los Molles Formation in the Neuquén Basin of Argentina are provided. In the study area, a high-resolution satellite image, drone imagery, and 30 logs (about 5000 m total thickness) were measured, focusing on facies analysis, paleocurrents, bed thicknesses, and large-scale thickness variations. Studies describing topographic confinement of sediment gravity flows have used five approaches: 1) Paleocurrent analysis: paleocurrents following structural trends and variations within the same bed (flow deflection and reflection). 2) Facies analysis: complex facies variations on short distances and increased number of hybrid beds and debrites near barriers (flow transformation), loading, convoluted structures, and bidirectional ripples (flow reflection), and sand–mud couplets or thick mudcaps (flow ponding). 3) Small-scale (decimeter to meter) thickness variations: beds thickening towards topography, beds thinning on top of topography (onlaps), and low thinning rates (loss of flow competence, flow containment). 4) Architectural analysis: aggradational stacking, lateral stacking away from topographic barriers, and fill–spill successions. 5) Large-scale thickness (tens of meters) variations: increased fan system thickness across topographic lows. An extended version of an existing classification scheme on degree of confinement is proposed: C0 (unconfined): no flow modification evidence present, and compensational stacking is a classic architectural pattern. C1 (weakly confined): variations in regional paleocurrent directions, minor thickness variations against small-relief barriers, large (basin scale) thickness variations. C2a (confined) to C2b (highly confined): onlaps against high-relief barriers, paleocurrent direction variations on the same bed, bed thickening against topography, facies evidencing flow reflection, increased number of hybrid beds, aggradational stacking, and high percentage of beds continuous over 500 m distances (tabular beds). C2a and C2b are considered end members of a spectrum where the amount of evidence listed can vary. C3 (ponded): sand mud couplets or thick mudcaps. Higher confinement categories might have indicators from the weaker confinement categories. The lower fan in the Los Molles Fm. turbidite system is classified as weakly confined. A complex sediment routing followed structural trends inherited from the rift phase of the basin. The basin-floor had irregular water depths that led to preferred sites of deposition. Hybrid beds are mostly found at the fringes of the lower part of the succession and might be associated with an above-grade slope profile on a footwall scarp. Lastly, the Los Molles Fm. basin-floor beds present high thinning rates (average 1.5 m/km) and the system stacks compensationally, pointing to null interaction against basin margins.

Verification of Tropical Cyclogenesis Forecasts of the Korean Integrated Model for 2020–21

Abstract Accurate tropical cyclogenesis (TCG) prediction is important because it allows national operational forecasting agencies to issue timely warnings and implement effective disaster prevention measures. In 2020, the Korea Meteorological Administration employed a self-developed operational model called the Korean Integrated Model (KIM). In this study, we verified KIM’s TCG forecast skill over the western North Pacific. Based on 9-day forecasts, TCG in the model was objectively detected and classified as well-predicted, early formation, late formation, miss, or false alarm by comparing their formation times and locations with those of 46 tropical cyclones (TCs) from June to November in 2020–21 documented by the Joint Typhoon Warning Center. The prediction of large-scale environmental conditions relevant to TCG was also evaluated. The results showed that the probability of KIM detection was comparable to or better than that of previously reported statistics of other numerical weather prediction models. The intrabasin comparison revealed that the probability of detection in the Philippine Sea was the highest, followed by the South China Sea and central Pacific. The best TCG prediction performance in the Philippine Sea was supported by unbiased forecasts in large-scale environments. The missed and false alarm cases in all three regions had the largest prediction biases in the large-scale lower-tropospheric relative vorticity. Excessive false alarms may be associated with prediction biases in the vertical gradient of equivalent potential temperature within the boundary layer. This study serves as a primary guide for national forecasters and is useful to model developers for further refinement of KIM.

Prediction of Structural Fracture Distribution and Analysis of Controlling Factors in a Passive Continental Margin Basin—An Example of a Clastic Reservoir in Basin A, South America

Structural fracture distribution is essential in oil and gas transportation and development in passive continental margin basins. In this paper, taking as an example the clastic reservoirs in the A-Basin, a passive continental margin in northeastern South America, the paleotectonic stress field of the Late Cretaceous Maastrichtian formation in Basin A was numerically simulated by finite element technique through the integrated interpretation of seismic total data, logging data and core data, and the distribution of tectonic fractures was later predicted based on rock fracture criterion. The results of the study show that: (1) The distribution of tectonic stress and fractures during the Late Cretaceous Maastrichtian formation of Basin A is affected by the fracture zone, mechanical properties of rocks and tectonic stress, regions with extensive fracture development are susceptible to stress concentrations, resulting in significant stress gradients. (2) The development of structural fractures in the study area was predicted using the Griffiths criterion, and the tensile rupture coefficient T was introduced to quantitatively characterise the intensity of fracture development, with larger values reflecting a higher degree of fracture development. The well-developed and relatively well-developed fractures are mainly located in the fracture zones and the interior of submarine fans. (3) Fracture zones and sedimentary phases mainly control structural fractures in Basin A; within 5 km outside the fracture zones, the development of fractures is controlled by the fracture zones, beyond which the regional tectonic stress field controls them; inside the sedimentary fan, the development of fractures is controlled by the sedimentary subphase, which decreases in the order of the upper fan, the middle fan, and the lower fan; inside the subphase, they are controlled by the regional tectonic stress field, and the fractures show the increasing trend in the direction of NW-NE.

Carboniferous–Permian interglacial warming and volcanism temporally linked to the world's oldest alkaline lake deposit of the Fengcheng Formation, NW China

In addition to being an important lacustrine hydrocarbon source rock, the Fengcheng Formation possesses well-preserved sodium‑carbonate evaporite units and tuff beds. Known ancient alkaline salt-lake deposits bearing sodium‑carbonate evaporite minerals like the Late Paleozoic Fengcheng Formation are limited beyond the modern day. However, hitherto the absolute age of the alkaline lacustrine Fengcheng Formation of the Junggar Basin (China) is debated (Late Carboniferous and/or Early Permian), and therefore its temporal link to a specific stage of the Late Paleozoic Ice Age (LPIA) remains unclear. Here, new ReOs geochronology demonstrates that the Fengcheng Formation is predominately of Late Carboniferous-age (304.4 to 297.3 Ma), and therefore its deposition coincides with the interglacial climate warming interval between glaciation C4 and P1 of the LPIA and not the younger interglacial stages as previously proposed. The ReOs isotope systematics indicate that the lake water column during the deposition of the Fengcheng Formation had a relatively unradiogenic Os (187Os/188Os, Osi) isotope composition (0.32 to 0.36), which is in contrast to the typical radiogenic Osi recorded for lacustrine deposits throughout geological time. The unradiogenic Osi for the Fengcheng Formation ties the source of the Os in the lake to the weathering of adjacent mafic volcanic rocks and/or hydrothermal input (∼0.13). As a result, the penecontemporaneous relationship to the Late Paleozoic interglacial climate warming (causing enhanced evaporation) coupled with weathering of volcanic rocks and/or hydrothermal fluid input into the lake is considered to have been mechanistic in the formation of an alkaline salt lake dominated by sodium and carbonate.

First record of Aegyptobatus (Hybodontiformes: Distobatidae) in the Cretaceous Alcântara formation (?Albian-Cenomanian) of Maranhão, Northeastern Brazil

ABSTRACT Hybodontiformes are considered the closest relatives of modern sharks and were the dominant shark group throughout most of the Mesozoic. Although, originally a marine group, during their long temporal range, they conquered the freshwater environment. This is the case of numerous taxa known in northern Gondwana. Here, we report the presence of the hybodontiform Aegyptobatus in the Albian-Cenomanian Alcântara Formation of the São Luis Basin, Northeastern Brazil. A comparison made with other hybodontiform teeth from the Northern Gondwana suggests that the teeth from the Alcântara Formation is noticeably the same species found in the late Cenomanian Bahariya Formation of Egypt, A. kuehnei. Although probably restricted to freshwater, the new discovery increases the geographic range of this taxon, adds one more common taxon between the Brazilian Alcântara Formation and Cretaceous units of North Africa, and extends the temporal range of this taxon down into the Albian-Cenomanian.

Novel pterygotid sea scorpions from the Silurian and Devonian of Gondwana

Sea scorpions (eurypterids) are a group of extinct aquatic chelicerates that have a fossil record spanning the Ordovician through to the end Permian extinction. Due to their size and preservational potential, eurypterids have been well-documented in European and North American deposits, with less evidence from Gondwana. There is particularly limited evidence of the group from the Australian fossil record. To rectify this, we report new examples of pterygotid eurypterids from the late Silurian Wallace Shale and Early Devonian Merrimerriwa Formation, Mulga Downs Group in New South Wales. These specimens are assigned to Pterygotus sp. (Wallace Shale) and Jaekelopterus c.f. rhenaniae (Merrimerriwa Formation, Mulga Downs Group). The material is used to explore the extensive distribution and dispersal of these large, pelagic eurypterids and consider the position of the animals in their respective paleoecosystems. We conclude that these new records evidence the diversity of larger arthropods in Australian deposits and that ongoing documentation of these rare fossils is required to further understand the Paleozoic of Australia.

A new theropod dinosaur from the Callovian Balabansai Formation of Kyrgyzstan

Abstract Recent fieldwork in the late Middle Jurassic Balabansai Formation of Kyrgyzstan has yielded a partial skeleton of a large theropod dinosaur. The material includes a few bones of the skull (postorbital, quadratojugal), dorsal and sacral vertebrae, fragments of the pectoral girdle and forelimbs, and an almost complete pelvic girdle and hindlimbs, and is here made the type of a new theropod taxon, Alpkarakush kyrgyzicus gen. et sp. nov. Alpkarakush can be diagnosed by an extremely developed orbital brow on the postorbital, a pneumatic opening leading into cavities in the neural arch from the centroprezygodiapophyseal fossa in the posterior dorsal vertebrae, an almost enclosed ventral sulcus in manual phalanx II-1, a narrow and deep intercondylar groove on the anterior side of the distal femur, and an epicondylar crest on the distal femur that is offset from the distal end. A second, fragmentary, and smaller specimen from the same site represents the same taxon. Based on long bone histology, the type of Alpkarakush represents a late subadult individual, whereas the smaller specimen is a juvenile, possibly indicating gregarious behaviour. Phylogenetic analysis places Alpkarakush in the Metriacanthosauridae, underlining the diversity and wide distribution of this clade in the Jurassic of Asia.

Magma mingling in plagiogranites of the Oman ophiolite suggests an origin by fractional crystallisation

Late-stage plagiogranites in the Oman-UAE ophiolite are frequently associated with layered and massive gabbro bodies, intrusive into the mid-crustal section of the ophiolite. This study reports persuasive field evidence from five different localities for magma-mingling between plagiogranites and melts with a mafic and dioritic composition. It is argued from these relationships that mafic and felsic magmas coexisted in the same magma chamber. On this basis it is suggested that the range of melt compositions is related by a process of fractional crystallisation. The plagiogranites are interpreted as the end-product of this fractionation process and the associated gabbros are thought to be related cumulates. The hypothesis is supported with geochemical evidence which shows from the major element chemistry a continuum of compositions between the most mafic and felsic endmembers (47.6–80.6 wt% SiO2). These compositions ‘capture’ the fractionation process in operation. Modelling these variations using the major and trace element chemistry indicates that the fractionating assemblage comprised olivine-clinopyroxene-plagioclase+/−amphibole and that some plagiogranites contained cumulus plagioclase. The mafic rocks associated with late stage plagiogranite formation are derived from a highly depleted mantle source, which implies melting of an already-depleted mantle. This is consistent with previous models for the origin of the Oman ophiolite and implies a supra-subduction setting for this phase of ocean crust evolution in this ophiolite.

Palaeoenvironmental implications of a turritelline-dominated assemblage from Upper Cretaceous carbonate rocks of Narmada Basin, India

Turritelline-dominated assemblages (TDAs) occur in modern siliciclastic seas within shallow depths, under normal to below normal salinity, high nutrient flux, high ocean upwelling current and/or runoff and cool water conditions. Similar assemblages in carbonate sediments are rare in modern oceans. However, TDA in carbonate rocks are common during the Cretaceous. In this study, we report the presence of a TDA in the late Turonian Nodular Limestone Formation of the Bagh Group, Narmada Basin, central India. An unusually small species of Turritella, T. bardhani Halder, n. sp., is described from the TDA. The TDA, in terms of host rock microfacies and taphonomy, indicates shallow water to intertidal, low to moderate energy, eutrophic to mesotrophic conditions, that prevailed in restricted lagoonal to marginal lagoonal, back-reef environments. The turritellines, based on trace elements and Rare Earth Elements concentration, thrived under dysoxic conditions and experienced above-normal marine salinities. The preferences of modern TDAs do not fully represent such past ecological and lithological conditions, indicating an example of a non-uniformitarian shift in habitat.

Mercury isotopes of the Late Ordovician to Middle Triassic tuff layers in South China link the fate of ancient volcanism and the mass extinction

Mercury (Hg) anomalies in sedimentary records are a newly developed proxy of large volcanism in the geological past. Tuff layers host abundant volcanic ash and record key information on the type of volcanic emission (e.g., arc volcanism and large igneous province eruptions). Here, we measured the Hg isotopic compositions of several tuff layers in South China. Tuff samples in the Late Ordovician Wufeng Formation and the Middle Triassic Guanling Formation mostly show positive Δ199Hg values of – 0.01 to 0.10‰ and – 0.06 to 0.16‰, respectively, suggesting arc volcanism occurred during these two periods. Tuff samples in the Middle Permian Dachang Layer mostly show near-zero Δ199Hg values (– 0.08 to 0.00‰), suggesting volcanism was driven by the Emeishan large igneous province eruption. Results of this study verify Hg isotopes as a useful proxy in revealing the type of volcanism in geological history.

Study of Pore–Throat Structure in Tight Triassic Sandstone: A Case Study on the Late Triassic Yanchang Formation, Southwestern Ordos Basin, China

In order to better understand pore–throat structure characteristics, the coupling relationship between micropore–throat structure and macro reservoir quality and influencing factors caused by authigenic minerals were studied. Petrographic analyses, scanning electron microscopy (SEM), pressure-controlled mercury injection (PMI), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) were performed on a suite of tight reservoir samples from the Chang 8 Member of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin, China. The results show that the pore–throat sizes obtained with the combination of PMI and NMR methods varied from nano- to microscale, revealing pore–throat sizes ranging from 0.001 μm to 70 μm, and showing that pore–throats with a radius larger than 1.0 μm are rare. Larger pore–throats with good connectivity (&gt;rapex) account for a smaller part of the total pore volume, ranging from approximately 7.58% to 38.90% with an average of 22.77%, but account for more than 80% of contributions to permeability. The effective movable fluid porosity (φemp) measured by NMR, ranging from approximately 0.10% to 7.07% with an average of 2.56%, had a positive contribution to permeability. The contents of chlorite occurrence state, other than illite, are beneficial to pore–throat preservation. A new reservoir evaluation scheme of the Chang 8 reservoir is established. These research results provide a theoretical basis for the evaluation and development of tight sandstone oil and gas exploration.

U‐Pb Geochronology of Paleosol Carbonate Cements by LA‐ICP‐MS: A Proof of Concept and Strategy for Dating the Terrestrial Record

AbstractThis study investigates the potential of laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) U‐Pb dating for carbonate nodules in the Late Triassic Ischigualasto Formation of northwestern Argentina. We establish a fully characterized paragenetic sequence to guide the analysis of three pedogenic carbonates and compare the U‐Pb ages with published geochronology from volcanic ashes within the sedimentary succession. Our findings demonstrate the importance of interpreting U‐Pb data within a well‐defined paragenetic framework for accurate age interpretation of pedogenic carbonates. We observe variations in U‐Pb isotopic signatures across different generations of carbonate precipitates and identify syn‐pedogenic and early burial calcite cements as most suitable for precise dating. Respectively, these two calcite cements are interpreted as microcodium and crack‐lining calcite cements formed early in the paragenetic sequence during pedogenesis to early burial of the paleosols as they transitioned from the unsaturated vadose to saturated phreatic zone below the water table. The U‐Pb ages obtained from the carbonate nodules agree with the radioisotopic ages of volcanic ashes, supporting the validity of our dating strategy. These results contribute to advancing U‐Pb carbonate geochronology and highlight its increased potential for dating sedimentary records in the terrestrial realm. Future research should focus on replicating similar work on different carbonate nodules within the Ischigualasto Fm and expanding the application of LA‐ICP‐MS U‐Pb dating to other carbonate‐bearing formations, especially in successions with limited absolute ages or where volcanic ashes are sparse or absent.